The long-term research goals of our laboratory center on defining signaling events in the microcirculation that underlie the control of oxygen and nutrient delivery to tissue with an emphasis on skeletal muscle during exercise. My working hypothesis is that the local control of blood flow reflects the coordination of activity among endothelial cells (ECs) and smooth muscle cell (SMCs) of arterioles and feed arteries (FA) that comprise microvascular resistance networks. When delivered to a discrete site on an arteriole or FA, acetylcholine (ACh; the gold standard endothelium-dependent vasodilator) initiates a Ca+2 wave that travels from EC to EC for hundreds of microns along the intima to promote relaxation of surrounding SMCs by releasing nitric oxide. However little is known of how calcium waves are initiated or propagated in the microcirculation. To directly address this question, I have developed the intact endothelial tube preparation from mouse abdominal muscle feed arteries as a unique model to study the nature of Ca+2 waves independent from the influence of blood flow, transmural pressure, or surrounding SMCs and tissue. Intact microvascular endothelial tubes (diameter, 50-80 5m; length, 1-2 mm) are isolated using microdissection of FA followed by partial enzymatic digestion and gentle trituration. Preliminary studies with dye transfer confirm that ECs throughout the tube are well-coupled through gap junctions and generate robust Ca+2 waves in response to ACh that can propagate more than 500 5m along the tube. My research is focused on understanding how these Ca+2 waves are initiated and how they actually propagate from EC to EC. AIM 1 will identify the source(s) of Ca+2 for wave initiation and propagation by preferentially inhibiting internal release of Ca+2 from the endoplasmic reticulum (ER) and/or its influx across the plasma membrane. AIM 2 will investigate how partial depletion or overloading of intracellular Ca+2 stores affects the initiation and propagation of Ca+2 waves. Resolving the role(s) of intra- and extracellular Ca+2 sources in producing waves will provide new insight concerning how these signaling pathways may contribute to the local regulation of blood flow. In turn, this knowledge will lead to a better understanding of how intrinsic Ca+2 signaling pathways may be altered during such conditions as atherosclerosis, diabetes, hypertension, and ischemia. My overall goal is to apply the findings of this research to the development of novel strategies for treating vascular disease in which tissue perfusion is impaired.